Effects of Various Potassium Fertilizer Dosages on Agronomic and Economic Assessment of Sweet Potato Fields

To explore the effects of various potassium fertilizer dosages on sweet potatoes, field experiments were conducted in 2018 and 2019 using a randomized block design. In the experiment, the control (completely blank, no fertilizer), KS0 (potassium blank, no potassium fertilizer), KS100 (100 kg K2O ha−1), KS200 (200 K2O ha−1), and KS300 (300 K2O ha−1) treatments were set up. The application of potassium fertilizer increased the potassium content of sweet potato plants, thereby increasing the chlorophyll content, net photosynthetic rate, and the fluorescence chlorophyll parameters. It also increased the amylose content in tuber roots to increase the total starch content and yield of sweet potatoes. Specifically, the KS200 treatment significantly improved the soil potassium content, potassium absorption, potassium agronomic efficiency, and potassium recovery efficiency. Compared with the other treatments, the yield and net profit of the KS200 treatment increased by 0.89–27.05% and 2.34–30%, respectively, on average, over two years. Based on factors such as sweet potato yield and starch content, the recommended amount of potassium fertilizer was 200 kg ha−1, which has significant economic benefits and theoretical value.